Tracking vibrations in a pipeline network

ABSTRACT

Tracking vibrations on a pipeline network includes installing multiple vibration recorders on the pipeline network, with each recorder including a sensor, a timer, a processor, and a digital communication device. At each vibration recorder, vibration signals are received from the sensor at programmed times under the control of the processor of the vibration recorders and processed by the processor. The processed vibration signals are communicated from the vibration recorder to a reader device using the digital communication device. Thereafter, the processed vibration signals from the one or more reader devices are collected at a central computer system. Finally, the collected processed vibrations signals are analyzed at the central computer system to determine abnormal vibration patterns and to obtain measures of any leaks present in the pipeline network.

TECHNICAL FIELD

This description relates to tracking vibrations in a pipeline network.

BACKGROUND

Pipeline networks are commonly used to distribute fluids, such as water,natural gas, petroleum, and jet fuel. Undetected leaks in such pipelinenetworks may be expensive and, potentially, hazardous.

SUMMARY

A provided system may include a set of many low-cost, intelligentvibration recorders that are permanently installed on a pipelinenetwork. Each recorder is capable of sensing, timing, processing, anddigitally communicating. The recorder is maintenance-free and isprogrammed to record vibration data every night from an associatedpipeline and to respond to a radio signal from a reader.

When a leak is present in a pipe, a pressure wave emanates from theturbulent source of the leak and travels away from the leak through thewall of the pipe and the fluid in the pipe. This leak signal isattenuated with distance and has a spectral signature (varying energy atdifferent frequencies) that depends on the effective transfer functionof the pipe network and the sensor connection. The effective range ofthe recorder depends on such factors as the pipe pressure, the leaksignal strength and the variable background pipe flow and ambient noiselevels present at the sensor.

Aspects of the system include installing the recorders on the pipelinenetwork, recording and processing in the recorders, data transport fromthe recorder to a database using the reader and the controller, dataanalysis in the computer, and visual presentation of the analysis.

Water and other utility companies manage capital and operationalexpenditures, often with capital expenditures being more available thanoperational expenditures. Leak detection will yield significant savingsin the form of reduced requirement for treatment and plant capacity,lost product, mandatory water use (revenue) restriction due to limitedwater resources, and reduced risk of catastrophic events. The challengefor water companies is to manage their human and capital resources toachieve sustainable network and leakage management. Currently, leakdetection is performed in the field using personnel, vehicles andcomputerized leak detection and pinpointing equipment. The completesystem, including recorders, readers, and controllers, provides theinformation needed to focus this effort with no additional operationalexpenditures.

In one general aspect, tracking vibrations on a pipeline networkincludes installing multiple vibration recorders on the pipelinenetwork. Each vibration recorder includes a sensor, a timer, aprocessor, and a communication device. At each vibration recorder,vibration signals are received from the sensor at programmed times underthe control of the processor of the vibration recorder, and the receivedvibration signals are processed by the processor of the vibrationrecorder. Processed vibrations signals are communicated from thevibration recorders to one or more reader devices using thecommunication devices of the vibration recorders. The processedvibration signals are collected from the one or more reader devices at acentral computer system that analyzes the collected processed vibrationsignals to determine abnormal vibration patterns and to obtain measuresof any leaks present in the pipeline network.

Implementations may include one or more of the following features. Forexample, a vibration recorder may include a housing, and installing thevibration recorder may include securing the vibration recorder to a pipeof the pipeline network using one or more O-rings that extend around thepipe and engage the housing. The vibration recorder may be a componentof a flow meter. A sensor of the vibration recorder may be a piezo-filmsensing element oriented in the housing so as to be at a knownorientation to a flow in a pipe when the vibration recorder is installedon the pipe.

Processing the received vibration signals may include tracking thereceived vibration signals over time. Tracking the received vibrationsignals over time may include computing a weighted average of thereceived vibration signals over a first period of time, and may furtherinclude computing a weighted average of the received vibration signalsover a second period of time having a duration that differs from aduration of the first period of time. Processing the received vibrationsignals also may include determining a distribution of a parameter ofthe received vibration signals.

Communicating processed vibrations signals from a vibration recorder toa reader device may include doing so in response to a command sent fromthe reader device or from a device to which the vibration recorder isconnected. The processed vibrations signals may be communicated using awireless communications channel.

The pipeline network may be a water pipeline network, and a meter readermay carry a reader device such that communicating processed vibrationssignals from a vibration recorder to a reader device includes doing soin conjunction with a normal process of having the meter reader read awater meter.

Collecting the processed vibrations signals from a reader device at thecentral computer system may include connecting the reader device to thecentral computer system and downloading the processed vibration signalsfrom the reader device to the central computer system. Communicationsbetween the reader device and the central computer may include using awireless communication channel.

Analyzing the collected processed vibration signals may includecomputing a leak index for a vibration recorder using processedvibration signals from the vibration recorder. Computing the leak indexfor the vibration recorder also may include using processed vibrationsignals from one or more additional vibration recorders. A leak statusmay be assigned to a vibration recorder using the leak index computedfor the vibration recorder. Computing the leak index may include usingknown information about the pipeline network, such as an estimate of theapproximate prevalence of leakage in the pipeline network. The leakindex may be displayed using a solid color map. The leak status of oneor more recorders may be represented graphically by using differentcolors. A graph showing a history or a statistical or nighttimedistribution of processed vibration signals may be generated.

The details of one or more implementations are set forth in theaccompanying drawings and the description below. Other features will beapparent from the description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of a system for tracking vibrations in apipeline network.

FIG. 2 is a block diagram of the data cycle for the system of FIG. 1.

FIG. 3 is a block diagram of a recorder of the system of FIG. 1.

FIGS. 4 and 5 are perspective views showing mounting of the recorder ofFIG. 3 on a pipe.

FIG. 6 is a graph showing an example of the nighttime distribution ofthe recorded vibration level from a single recorder.

FIG. 7 is a graph showing an example of the nighttime recorded vibrationlevel from a single recorder.

FIG. 8 is a block diagram of a reader of the system of FIG. 1.

FIG. 9 is a block diagram of a controller of the system of FIG. 1.

FIG. 10 is a graph showing a distribution of a leak index among all therecorders in a system.

FIG. 11 is a map with symbols used to represent the positions ofrecorders on the map.

FIG. 12 is a solid color map showing a value of a leak index at alllocations on the map.

FIG. 13 is a graph showing the vibration level history of a singlerecorder of the system of FIG. 1.

FIG. 14 is a database table showing parameters of the recorders.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

Referring to FIG. 1, a system 100 for tracking vibrations and detectingleaks in a pipeline network 105 includes recorders 110 connected to thepipeline network 105. The recorders 110 collect data about vibrations inthe pipeline network. One or more readers 115, when brought intoproximity with the recorders 110, collect data from the recorders 110.The one or more readers 115 later download data to a computer 120, suchas a personal computer (or PC), that processes the data from multipleloggers to detect vibrations and related phenomena (e.g. leaks) in thepipeline network 105.

While the pipeline network 105 is described below in terms of a watersystem, the pipeline may be another type of network. For example, thesystem may function with other pressurized fluid-carrying pipelinenetworks, such as those carrying natural gas, petroleum, and jet fuel.

In general, the recorders 110 are vibration recorders installedpermanently on the pipeline network 105. For example, when the pipelinenetwork 105 is a water network, the recorders may be installedpermanently on water service lines, typically near the water meter ineither meter pits or basements. In some implementations, a recorder 110may be included as part of a water meter. In a gas distribution system,the recorders may be installed permanently on gas service lines,typically near the gas meter. In other networks, such as transmissionlines, the recorders may be installed at valves, other convenient accesspoints, or on the pipeline itself. The installation may be undergroundor above ground, depending on the construction of the pipeline and thefacilities needed to communicate with the recorder.

In summary, and referring to FIG. 2, the data cycle for the system 100begins with a leak generating vibrations (200). The sensor of therecorder generates a vibration signal corresponding to the vibrations(205) and the recorder generates data corresponding to the vibrationsignal (210). From time to time, a reader collects the data from therecorder (215). This data then is transported from the reader to acomputer through a radio or other link. (220). Software on the computerprocesses the data to identify leaks and generate corresponding reports(225). Repair personnel then use other systems, such as the DigiCorrsystem available from Flow Metrix, Inc., to confirm and pinpointlocations of the leaks (230). Finally, the pinpointed leaks are repaired(235).

Referring to FIG. 3, each recorder 110 includes a vibration sensor 300,signal conditioning electronics 305, a processor 310, a battery powersupply 315, and a low-power radio transceiver 320. The sensor 300 maybe, for example, a piezo-film sensor, a piezo-cable sensor, or someother low-cost vibration sensor. The sensor 300 produces an electricalsignal reflective of vibrations in the pipe to which the sensor isattached.

In colder climates, recorders are installed at the water meter,typically in a basement. In warmer climates, recorders are installedoutdoors in an underground water meter pit. Recorders have aninstallation density designed to match the expected incidence ofleakage. Most leaks occur on service pipes. Typical installations may be10 per mile (one every 500 feet) or one per 10 services, depending onthe terrain. Installations will be more dense in downtown areas and lessdense in rural areas. In general, the density of installations may beapproximately proportional either to the length of the pipeline networkor to the number of services on the network.

Installation is a significant logistical exercise and can be performedas part of a water meter upgrade program. As shown in FIGS. 4 and 5, therecorder 110 is mounted to a pipe 400 by two O-rings 405 that resistweathering and corrosion, require no tools and are easily and quicklyfitted to the pipe. As shown, the housing 410 of the recorder includesconnection points 415 that support attachment of the O-rings. Inaddition, the housing 410 includes curved brackets 420 that easeengagement with the pipe.

A piezo-film vibration sensor, the sensor employed in someimplementations, is capable of registering ultra-low vibration levels,but must be directionally-oriented in the line of the flow. The housingdesign ensures this orientation when installed. Upon installation, therecorder is started with a radio signal from a specially programmedreader.

The signal conditioning electronics 305 receive the signal from thesensor 300, adjust the signal, and pass the adjusted signal to theprocessor 310. For example, the signal conditioning electronics 305 maybe configured to use highpass filtering to reject low frequencyvibrations that are present on the pipeline but generally are notproduced by leakage. The signal conditioning electronics 305 may befurther configured to reject high frequency vibrations through the useof lowpass filtering to improve the signal-to-noise ratio of thevibration recording by restricting high-frequency electronic noise. Thesignal conditioning electronics 305 also provide analog gain to amplifythe signal received from the sensor to a level suitable for digitizing.The degree of analog gain may optionally be set under digital control ofthe processor 310. The amplified and filtered signal is digitized, usingwell-known digitizing techniques, either within the signal conditioningelectronics 305 or within the processor 310.

The processor 310 generates data representative of the detectedvibrations. The processor then stores the data for later transmissionusing the transceiver 320. The transceiver 320 may be a digital radiotransceiver operating at 916 MHz.

The power supply 315 powers the electronic components of the recorder110. In one implementation, the power supply includes two AA alkalinebatteries that provide sufficient power for ten years of recorderoperation.

The recorder records and processes a series of recordings every night tocreate a useful representation of the nighttime vibrations. During thenight, leak signals are maximized due to minimal usage flow and hencemaximal pipe pressure. Background and ambient noise is also minimal. Thenighttime representation aims to exclude transient vibrations due towater usage or background noise and to characterize the pipe vibrationspresent during the quietest part of the night, whenever this occurs. Thesignal generated at the quietest point of the night may be referred toas the quiescent pipe signal.

Referring to FIG. 6, a graph 450 shows a possible distribution of therecorded vibration level, sampled at many times during a single night bya single recorder. Visualizing the distribution of the recordedvibration level allows interpretation of the nighttime vibrationactivity. For example, as shown in FIG. 6, background vibration activitymay be represented by the apparent normal distribution with mean μ₁ andstandard deviation σ₁. When leakage is present, the mean vibration levelμ₁ may be high compared to situations where leakage is not present andthe standard deviation of the background vibration activity σ₁ will tendto be small compared to μ₁ and compared to situations where leakage isnot present. Background vibration activity may include transient orsporadic events from causes such as irrigation systems (sprinklers),nighttime usage, pumps, and other vibration sources. The graph 450 showsa possible bi-modal distribution which includes the effects of thistransient activity represented by the apparent normal distribution withmean μ₂ and standard deviation σ₂. Other forms of the distribution ofnighttime vibration activity may occur, including for example, a widenedor skewed distribution, or activity that follows a non-normal parametricor a non-parametric distribution.

Referring to FIG. 7, the nighttime vibration activity also may be shownas a graph 460 that expresses the relationship between the vibrationlevel and the time of day. A minimum vibration level is presumed tooccur at some time during the night and corresponds to the quiescentpipe signal. Visualizing the nighttime activity as a time series allowsinterpretation of continuous and transient aspects of the nighttimevibration activity.

Other advantages of the visualization capabilities shown in FIGS. 6 and7 are apparent. For example, unintended usage such as drawing water fromfire systems may be detected from examination of the recordedvibrations. The theft or unauthorized usage of product from water, gas,petroleum, or other pipelines may also be detected from examination ofthe recorded vibrations. Other applications of the system are readilyapparent. For example, the recorded vibrations can be used to documentand visualize an approximate usage profile of product at a particularpoint from a pipeline over a particular time period. Comparison ofrecordings from two or more such time periods can be used to detectchanges in the usage profile at a particular point from a pipeline.

The representation of nighttime vibrations may include, but is notlimited to, the following parameters: absolute vibration level of thequiescent pipe signal, frequency content of the quiescent pipe signal,distribution of frequency content during the nighttime period, and acomparative measure of these parameters with what has been historicallyrecorded. The goal of the signal processing is to reduce the availablenighttime data (30 million bytes for two hours at 4,000 samples persecond and one byte per sample) to a characterization or compression ofthe useful information contained within 64 to 4096 bytes.

Referring again to FIG. 1, in one implementation, each recorder 110independently makes a series of vibration recordings every night. Ingeneral, a recorder may be able to sense vibrations from a distance ofup to 500 feet or greater. The recordings are processed to produce auseful representation of the nighttime vibration levels. For example,the recorder 110 may be configured to monitor vibrations at night,process the monitored vibrations, and enter a low-power SLEEP stateduring the day and at all times when not recording or communicating.

In one implementation, vibration signals are digitized by the processor210 at a sampling rate of 2,048 Hz. Recording begins at 12:15 am andoccurs once per minute until 4:30 am for a total of K=256 recordings.Each recording lasts for one second and is denoted by x_(k) (i), where kis the recording number and i is the sample number within the recording.Vibrations from pipes typically manifest as pseudo-random stochasticprocesses, sometimes with a specific spectral structure. Accordingly,each recording may be statistically processed to extract usefulinformation with a reduced storage requirement. One useful method is tocompute the mean absolute value of the recording, defined as:${E\left\lbrack {{x_{k}(i)}} \right\rbrack} = {{\sum\limits_{i = 1}^{N}{{{x_{k}(i)}}/N}} = \overset{\_}{x_{k}}}$where E[] represents mathematical expected value and the recording iscomposed of N=2048 samples. If it is assumed that the pipe vibrationsignal follows a statistically normal distribution, then the values of|x_(k)| resulting from each of the K recordings will follow astatistical chi-square distribution. It is useful to define thefollowing quantities:$\mu_{q} = {\sum\limits_{i = 1}^{N}{\overset{\_}{x_{k}}/K}}$ and$\sigma_{q} = \sqrt{\sum\limits_{k = 1}^{K}{\left( {\overset{\_}{x_{k}} - \mu_{q}} \right)^{2}/K}}$where μ_(q) and σ_(q) are, respectively, the mean and standard deviationof this assumed chi-square distribution considered for the ensemble of Krecordings made on day q. In the presence only of flow noise, it hasbeen determined that the relationship between μ_(q) and σ_(q) isspecific, namely that μ_(q) is approximately equal to σ_(q) . In thepresence of vibrations due to leakage or transient phenomena, thedistribution may no longer follow an approximate chi-square form. Inthis instance, it is useful to store enough information to approximatethe form of the distribution of |x_(k)|. One example of such anapproximation is to compute the values of the bins of a histogram thatapproximately follows the distribution of |x_(k)|. This procedure firstdefines the boundaries of 2p bins as μ_(q−1)±n a σ_(q−1,), where nranges from 1 to p and a is a constant, e.g. 0.2. By counting the numberof occurrences when |x_(k)| falls within each bin, either a parametricor a non-parametric distribution for |x_(k)| may be approximated. Thevalues of μ_(q−1) and σ_(q−1) are used as a starting point for thedistribution computed on day q. This assumes that the mean and standarddeviation of the distribution may not differ significantly from day q−1to the following day, q.

Another useful reduction of the set of vibration recordings is the valueof |x_(k)| corresponding to either the quietest or some other desirablecharacteristic of any recording made during the night. This parametermay correspond to the quiescent pipe signal and may be termed thequiescent parameter. The quiescent parameter will be useful assumingthat the recording duration is sufficiently long that X_(k) (i) can beconsidered an accurate reflection of the pipe vibration signal presentat recording time k. Alternatively, a useful subensemble of the ensembleof K values of |x_(k)| may be used to compute the quiescent parameter.For example, it may be useful to compute the quiescent parameter byaveraging a number of values of |x_(k)| corresponding to, for example,the quietest recordings made during the night.

Pipe vibration signals may contain different energies at differentfrequencies. It is useful to form a representation of the variation ofvibration energy versus frequency, denoted by X(m), where m representsdiscrete frequency. Many methods exist for estimating X(m). Theseinclude application of the Fourier transform, application of othernumerical transforms, processing the recorded data with differenceequations to empnasize a parucuiar frequency band, and other well-knownnumerical digital signal processing methods. Segmentation of the pipevibration signal into one or more discrete frequency bands can allow adiscrimination of signal components. For example, X_(k) (i) can besegmented into x_(k) ^(v) (i), where v ranges from 1 to V and representsa number of discrete frequency bands. These bands may be determinedusing a so-called basis set, including for example an octave filter bankor a wavelet transform. All of the processing methods described aboveand performed with x_(k) (i). may equally well be performed with X_(k)^(v) (i) (i.e. discrete frequency bands of the pipe vibration signal maybe processed individually or jointly).

Due to the stochastic nature of pipe vibration signals and the transientnature of other vibrations, the parameters described above may notalways be reliable indicators of leakage and other vibration phenomena.An important aspect of the described techniques is the ability of therecorder to adapt to its environment. The recorder performs such anadaptation by taking into account the changes of vibration signalsexperienced over one or more nights. Any quantitative parameter, y,(including but not limited to the parameters described) may be trackedon a night-by-night basis as follows:${\overset{\_}{y}}_{q} = {{\frac{1}{R}y_{q}} + {\frac{R - 1}{R}{\overset{\_}{y}}_{q - 1}}}$where Y_(q) is the parameter to track on day q, R is the number of daysover which to track the parameter, and y _(q) is the weighted average ofthe parameter computed for day q. The variable R may be referred to asthe tracking period, measured in days. If the parameter being tracked,y, is, for example, vibration level, and R is equal to 7, then y _(q)will be a weighted average of the vibration level over the last 7 days.The parameter y _(q) is thus useful because it effectively ‘remembers’the vibration level for up to 7 days. If the vibration level suddenlychanges on day q, then y _(q) can be usefully compared to y _(q) todetect this sudden change.

The variable R may also usefully be set to, for example, 14, 30, or 90days, or some other time period. Denoting the tracked parameter with thetracking period, R, as y _(q) ^(R) , a matrix of tracked parameters maybe defined with several different parameters, each tracked over severaldifferent tracking periods. The different tracking periods allowcomparison of the current value of any parameter, y_(q) , with itsweighted average value, y _(q) ^(R) , computed over R days. Thecomparison will be most sensitive to changes that have evolved overapproximately R days. For example, if a leak in a pipeline develops overthe course of a month, there may not be a significant change in aparameter y measured from night to night, however the comparison of y_(q) ³⁰ with y_(q) can be expected to be significant. Similarly y _(q)⁹⁰ may be expected to track seasonal changes in parametery.

This method of tracking a parameter offers several advantages. Forexample, updating and storing in the memory of the recorder a smallmatrix of parameters y, each recorded over a number of differenttracking periods R, obviates the need to store the values of individualparameters for every day. This is advantageous in that less power isrequired to transmit a smaller amount of data from the recorder and lessmemory is required in both the recorder and the reader. The trackingperiod R in the recorder may be programmed using the reader.

It is not necessary to program the recorder with specific rules fordetermining whether a particular characteristic of a parameter may beindicative of normal phenomena, including, for example normal flow,environmental noise, pump noise and other normal phenomena, or whetherthe parameter may be indicative of abnormal phenomena such as, forexample, leakage or unauthorized usage. The characteristics ofparameters generally vary unpredictably from pipe to pipe, from locationto location, and according to the season of the year, pressure,characteristics of the pipe, and other factors. For example, a moderateor loud vibration on a pipe may be due to higher flow, a larger pipe,construction occurring in the vicinity, a fire hydrant or pipelineflushing program, leakage, or some other cause. The method of trackingenables the recorder to adapt to its environment. The recorder is ableto provide both the parameters of the recorded vibrations and thetracking information, allowing subsequent analysis to interpret both,either individually or together. The method of tracking is thereforeable to take into account unexpected or unpredictable phenomenaoccurring either permanently or temporarily over any arbitrary timeperiod.

Water distribution systems often experience varying seasonal flows dueto irrigation and other seasonal demands. Similarly, gas distributionsystems often experience varying seasonal flows due to heating and otherseasonal demands. Another useful advantage of the method of tracking isto be able to perform seasonal adjustments to the recorders' data,thereby taking into account either predictable or unpredictablevariations occurring over any arbitrary time period.

Referring again to FIG. 1, a reader 115 is brought into proximity with arecorder 110 from time to time. For example, the reader 115 might becarried by a meter reader, mounted to a utility vehicle, or kept by ahomeowner. The reader 115 may be a device that, for example, weighsapproximately three ounces and is the size of a pager, or a deviceattached to or incorporated in a meter reading device.

Referring to FIG. 8, the reader includes a transponder 500, a processor505, a memory 510, a battery 515, and a computer connection 520. Thetransponder 500 periodically transmits (e.g. once every 10 seconds) aradio message that may be referred to as a broadcast ‘PING’. Forexample, in an implementation involving a water system, a meter readercarries a reader 115. This device transmits a frequent PING by radio towake up any recorders 110 within radio range. In one implementation, theradio range is 75 feet.

If the recorder receives this PING while in the low-power SLEEP state,the recorder wakes up and transmits an acknowledgement that includes therecorder's processed results. The reader 115 receives theacknowledgement and, under control of the processor 505, stores theprocessed results in memory 510. In one implementation, a reader hasstorage capacity for results from on the order of 16,000 differentrecorders. This data transport from the recorder to the reader iscompletely automatic and requires no special action on the part of themeter reader as he or she performs his or her normal tasks. Both therecorder and the reader manage power optimally so as to conserve thelife of the battery 315 (FIG. 3).

The reader 115 also may be operable to upgrade or modify the software ofa recorder through transmission of a message to the recorder. Thismessage may be transmitted in response to an acknowledgement receivedfrom the recorder.

The reader 115 may be connected to the computer 120 through the computerconnection 520, which may be a wired or wireless connection 520. Uponconnection, processed recorder results stored in the reader's memory 510are transmitted to the computer 120 for further processing. In oneimplementation, the transponder 500 also operates as the computerconnection 520.

For example, the meter reader may deposit the reader in the office atthe end of the working day. The processed data from all recordersvisited by one or more meter readers is now available in one or morereaders. The one or more readers may be connected directly to a computerat this point to transfer this data to a computerized database.

Referring to FIG. 9, the computer 120 may optionally include acontroller 550 that is operable to communicate with multiple readers 115to collect processed recorder results and deliver the processed recorderresults without human action. For a water company, for example, thisaccomplishes collecting vibration data from many service point locationsand bringing the data to a central computer with no human action otherthan that normally engaged in for the purposes of reading the watermeters.

The controller 550 may be a special form of reader 115 that iselectronically connected to a computer 120. During the night, thecomputer causes the controller to establish radio communication with allreaders present. The controller collects the data by radio from thereaders and transfers this data to a computerized database.

The computer 120 includes software that may be used to create aninformation profile for each recorder. This profile may includeinformation useful for maintaining the system, such as the deploymentdate, the last reading date, and the map/GPS location of the recorder,as well as information for interpreting the processed results, such asthe type and size of pipe on which the recorder is installed, the watermain connected to that pipe, the type of location (e.g. residential,industrial, urban or rural), and a leakage history for that area.

The software automatically computes a leak index (e.g. a value between 0and 100) for each recorder, using a combination of processed results andinformation profiles from one or more recorders. A leak status can beassigned by quantizing the leak index, with each leak status beingassigned a different color for display purposes. For example, a leakindex of 0-60 may be designated as representing no leak and assigned thecolor green, a leak index of 60-80 may be designated as representing apossible leak and assigned the color yellow, and a leak index of 80-100may be designated as representing a probable leak and assigned the colorred.

The leak index may be based on individual recorder processed results,such as absolute levels of vibration, consistent patterns of vibrationover time, gradually increasing levels of vibration over time, a suddenincrease in vibration levels, or changes in spectral composition of therecorded vibrations. These contributors are based on a prioriinformation (i.e. generally available knowledge about the relationshipbetween leaks and pipe vibrations).

The leak index also may be based on the processed results of a set orsubset of recorders, such as the loudest recorders; the recorders withthe widest frequency content; the recorders with the greatest changes inlevel or frequency content over a time period of, for example, 7, 30 or90 days; or the recorders within a subset, such as a type of location ora type of connected pipe, with processed results that are unusual (i.e.outliers in the statistical distribution of the subset). The leak indexmay be further impacted by network factors, such as leak size, sensitivelocation (e.g. museum basement), and known profile information, such asleakage history, the presumed likelihood of a leak at the recorder'slocation, and pipe size, age, and pressure.

Quantizing the leak index (0-100) to a leak status (green, yellow, red)aids leakage management. The quantization may be based on, for example,operations and maintenance resources. For example, in a 1,000-milenetwork, how many leak pinpointing investigations can be budgeted in ameter-reading cycle? The system can be set to generate a fixed number ofprobable leaks based on available resources (i.e. the system can beconfigured to detect the largest number of most likely leaks that can beinvestigated with available resources).

The quantization also may be based on leakage minimization so as toprovide the most leakage recovered per operating dollar spent. Thisapproach implies using all data to optimize the rate of true positiveleak identifications.

The quantization also may consider network optimization/leakagemanagement. In particular, the leak status may be set using the currentestimate of leakage density within the network as a whole. For example,consider a network with 1,000 miles of water mains, 100,000 meteredaccounts, and one recorder installed on average for every 10 meters,i.e. 10 recorders per mile. Assuming that the network has 500 leaks, thenetwork-wide probability of a recorder hearing a leak is approximatelyfive percent. On this basis, with a total of 10,000 recorders thepercentage of recorders assigned a leak status of red would be fivepercent of all recorders.

Referring to FIG. 10, a graph 600 illustrates the distribution of a leakindex (or any other quantitative parameter, such as vibration level)from all recorders or a subset of recorders. The graph 600 shows, as anexample, a statistically normal distribution of the leak index among allthe recorders in the system. The graph also shows approximately how manyrecorders are assigned a green, yellow, or red leak status according tothe particular quantization used to create the graph. Specifically,referring again to FIG. 10, the horizontal axis of the graph representsleak index values running from left to right. Each bar 610 representsthe number of recorders (the units of the vertical axis) occupying aparticular range of leak index values. The color of the bar (green,yellow, or red) represents the leak status of all recorders occupyingthe particular range of leak index values corresponding to that bar. Ifthe quantization relationship between the leak index (or anotherquantitative parameter used to create the graph) and the leak status ischanged, the approximate number of recorders assigned a particular leakstatus can be easily visualized.

It is often advantageous to present information about the leak status ofmany recorders in the context of maps showing the areas in which therecorders are installed. Referring to FIG. 11, a map 650 includessymbols 660 that represent the positions of recorders on the map. Thesymbols may be color-coded to display the leak status of the recordercorresponding to the symbol. The leak status may be programmed toreflect a quantization of the leak index or any other quantitativeparameter obtained from the recorders.

Another useful method of visualizing information from many recorders inthe context of maps showing the areas in which the recorders areinstalled is a solid color map. Referring to FIG. 12, a solid color map680 shows a value of a leak index (or another quantitative parameter) atall locations on the map. The color at each location on the map ismapped to a particular value of the leak index using a color scale 690.With a solid color mapping of the leak index, the locations of allrecorders present on the map may be given the known leak index of thatrecorder. All other locations on the map may be given a computed valueof the leak index that is extrapolated from the known values of the leakindex of nearby recorders. This extrapolation may be performed using anumber of well-known algorithms.

The solid color map 680 may be updated at any time under softwarecontrol using, for example, an update button 695. The update feature isuseful for varying the map scale, and the number of recorders andgeographical area included in the solid color map. The solid color map680 allows visualizing the extent of vibrations recorded by one or morerecorders. The solid color map 680 may be useful in computing andvisualizing an approximate location of possible leaks using thevibration recordings of one or more recorders. The solid color map 680may be overlaid and merged with details of aerial photographs, citymaps, or maps of the pipeline system.

Each recorder may also have a stored history of processed data.Referring to FIG. 13, a graph of vibration level history 700 may displaya mean vibration level 705 together with a lower range measure 710 andan upper range measure 715. The lower and upper ranges may be computedfrom the history of processed data and represent estimates of thevariation of the vibration level relative to the mean vibration level.The lower and upper range elements may also be omitted. Any historicalquantitative parameter may be similarly displayed. The graph ofvibration level history 700 is useful for visualizing changes that mayhave occurred over any available period of time in the vibrationrecordings of one or more recorders.

It may also be useful to select recorders according to some criteriabased on the recorders' information profiles and processed vibrationdata. Referring to FIG. 14, a database table 800 may show parameters ofthe recorders, including for example, leak index, leak status, map,address, and remarks entered by the system user. These parameters may bearranged in a database table that can be printed or exported to othersoftware. Any subset of recorders can be defined, based on selectingparticular values, or ranges of values of the parameters that areorganized as the columns 810 of the database table 800. The columns maybe sorted in some useful order. Other database capabilities may beincorporated to aid in managing the installation or information profilesof the recorders, the analysis of the recorders' processed vibrationdata, or the investigation of leaks or other activity that will occur asa result of the analysis.

Reports may be generated electronically or may be printed in order toaid these management, analysis, and investigation activities. Thecomponents of a report may contain a map, a database table with selectedparameters from a set or subset of recorders, and other elements such asa title, date, or signature line that may aid the management, analysis,and investigation activities.

A number of implementations have been described. Nevertheless, it willbe understood that various modifications may be made. Accordingly, otherimplementations are within the scope of the following claims.

1-23. (canceled)
 24. A vibration recorder for tracking vibrations in apipeline network, the vibration recorder comprising: structure forinstalling the vibration recorder on the pipeline network, the structureincluding a mechanism for receiving an O-ring that extends around a pipeof the pipeline network so as to secure the vibration recorder to thepipe; a sensor that produces vibration signals representing vibrationsin the pipeline network; a communication device; and a processor thatreceives and processes vibration signals from the sensor and controlsthe communication device to communicate the processed vibration signals.25. The vibration recorder of claim 24, wherein the processor isprogrammed to store the vibration signals from the sensor.
 26. Thevibration recorder of claim 25, wherein the processor stores thevibration signals when a usage flow in the pipeline network is minimal.27. The vibration recorder of claim 24, wherein the processor controlsthe communication device to communicate the processed vibration signalsto an associated reader.
 28. The vibration recorder of claim 24, furthercomprising a housing, wherein the sensor comprises a sensing elementoriented in the housing so as to be at a known orientation to a flow ina pipe when the vibration recorder is installed on the pipe.
 29. Asystem for tracking vibrations in a pipeline network, the systemcomprising; two or more vibration recorders, wherein each of thevibration recorders comprises; structure for installing the vibrationrecorder on the pipeline network; a sensor that produces vibrationsignals representing vibrations in the pipeline network; a communicationdevice; and a processor that receives and processes vibration signalsfrom the sensor and controls the communication device to communicate theprocessed vibration signals; one or more reader devices configured toreceive the processed vibration signals from the communication devicesof the vibration recorders; and a computer system configured to collectthe processed vibration signals from the one or more reader devices andfurther process the processed vibration signals to determine abnormalvibration patterns and to obtain measures of any leaks present in thepipeline network.
 30. The system of claim 29, wherein the structure forinstalling the vibration recorder on the pipeline network includes amechanism for receiving an O-ring that extends around a pipe of thepipeline network so as to secure the vibration recorder to the pipe. 31.The system of claim 29, wherein at least one of the vibration recordersfurther comprises a housing and the sensor the at least one vibrationrecorder comprises a sensing element oriented in the housing so as to beat a known orientation to a flow in a pipe when the at least onevibration recorder is installed on the pipe.
 32. The system of claim 29,wherein the computer system is configured to computes a leak index for apredetermined location of the pipeline network.
 33. The system of claim32, wherein the computer system is configured to compute the leak indexusing known information about the pipeline network.
 34. The system ofclaim 33, wherein the known information comprises an estimate ofapproximate prevalence of leakage in the pipeline network.
 35. Thesystem of claim 32, wherein the computer system is configured to computethe leak index for the predetermined location using vibration signalsrepresenting vibration at different locations in the pipeline network.36. The system of claim 32, further comprising a display to display theleak index on a map.
 37. A flow meter including a vibration recorder fortracking vibrations in a pipeline network, the flow meter comprising; aflow sensor that measures flow in the pipeline network; a vibrationsensor that produces vibration signals representing vibrations in thepipeline network; a communication device; and a processor that receivesand processes vibration signals from the vibration sensor and controlsthe communication device to communicate the processed vibration signals.38. The flow meter of claim 37, wherein the processor is programmed tostore the vibration signals from the sensor.
 39. The flow meter of claim38, wherein the processor stores the vibration signals when a usage flowin the pipeline network is minimal.
 40. The flow meter of claim 37,wherein the processor controls the communication device to communicatethe processed vibration signals to an associated reader.